[GitHub] [arrow-datafusion] alamb opened a new issue #1692: Support predicate pruning on `CaseExpr` expressions

[GitBox <gi...@apache.org>]

alamb opened a new issue #1692:
URL: https://github.com/apache/arrow-datafusion/issues/1692


   **Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
   In certain situations , IOx is likely going to make predicates that look like the following
   
   ```sql
   CASE 
     WHEN col IS NULL THEN '' 
     ELSE col 
   END
   ```
   that basically map `null` to the empty string
   
   We would like to use such predicates in order to prune out Chunks (or parquet record groups)
   
   
   
   **Describe the solution you'd like**
   I would like `CaseExpr` to be added to the list of expression types supported by predicate pruning in `build_predicate_expression`:
   https://github.com/apache/arrow-datafusion/blob/03075d5f4b3fdfd8f82144fcd409418832a4bf69/datafusion/src/physical_optimizer/pruning.rs#L640-L699
   
   The tricky bit of this PR would be figuring out what the transformation is and in what circumstances it can be applied
   
   **Describe alternatives you've considered**
   A clear and concise description of any alternative solutions or features you've considered.
   
   **Additional context**
   See https://github.com/influxdata/influxdb_iox/pull/3557 for more details


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[GitHub] [arrow-datafusion] tustvold commented on issue #1692: Support predicate pruning on `Expr::Case` expressions

[GitBox <gi...@apache.org>]

tustvold commented on issue #1692:
URL: https://github.com/apache/arrow-datafusion/issues/1692#issuecomment-1025578145


   @alamb could you assign this ticket to me please :smile: 


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